Polymers are used in almost every product manufactured today. In polymer processing facilities where polymers are made, unwanted polymeric masses collect on the surfaces of the equipment during the polymerization process. For example, the inside surface of tube and shell heat exchangers become coated with polymeric masses. Such polymeric fouling of equipment causes a substantial loss of operational efficiency, and often such polymer-fouled equipment must be removed completely from operation.
In known methods of removing polymeric deposits, fouled equipment must be transported to a specialized facility where the polymer is burned off of the fouled surfaces in specially-constructed furnaces. Such furnace burn-out methods only clean the units transported into the furnace and not the fouled system as a whole. In such methods, the polymer-fouled equipment must be transported in and out of the plant, which occurs at considerable expense. Also adding to the time and expense of these methods are environmental and safety requirements that the polymer and equipment must be steamed to remove liquid solvents, which adhere to the contaminated surfaces or the equipment itself. After the equipment is put back into service, it is common for it to again be removed for cleaning after an average of only about four months.
In other known methods, it is attempted to remove polymer build-up mechanically with chain saws, hydro-blasting, or similar methods. Such methods are generally very costly, messy, time-consuming, and accompanied by significant safety risks. Often a film of polymer fouling will remain following use of these methods, which compromises heat transfer efficiency and promotes polymeric fouling re-seeding.
U.S. Pat. No. 6,644,326, which is incorporated by reference herein, describes a process for dissolving olefinic polymeric fouling from processing equipment using a low vapor pressure aromatic solvent, such as diphenylethane and ethylenated benzenes. A preferred solvent is Dowtherm Q (Dow® Chemical Company). This mixture is from about 50% W to about 66% W 1,1-diphenylethane and from about 34% W to about 50% W ethylenated benzenes.